In current human and animal medical practice, there are numerous instances where therapeutic or diagnostic agents must be delivered to a specific organ or tissue within the body. One example is the lengthy treatment period where chemotherapy is infused into a central vein on a recurring basis in an attempt to treat widespread sites of malignant tumors. Without a device for intravenous drug infusion, multiple vein punctures over a lengthy period of time would result in progressive thrombosis, venous sclerosis, and destruction of small diameter peripheral vessels. In other situations, it may be desirable to infuse chemotherapy to a localized malignant tumor site. Delivering an agent specifically to such a site on a regular repetitive basis without surgically implanting an infusion system would prove difficult if not impossible. Similarly, repeated arterial access is occasionally needed to inject an X-ray dye or contrast agent into an artery for diagnostic purposes. In still other situations, there is a need to repetitively remove a body fluid from a remote body site for analysis. Finally, sensing and physiological measuring devices incorporated into small diameter catheters and optical fibers are increasingly being utilized for monitoring body processes and could be more easily implemented through a properly designed access device with an adequate internal diameter.
In prior medical practice, percutaneous catheters have been used to provide vascular or organ access for drug therapy or the withdrawal of body fluids. Although such systems generally performed in a satisfactory manner, numerous problems were presented by such therapy approaches. These problems included, without limitation, the substantial care requirements of the patients, e.g. dressing changes with sterile techniques, a significant rate of infection of the catheter because of its transcutaneous position, and a high rate of venous thrombosis, particularly if the catheter was located within an extremity vein.
Implantable infusion devices or "ports" have recently become available and represent a significant advance over transcutaneous catheters. Presently available infusion ports have a number of common fundamental design features. The ports themselves comprise a housing which forms a reservoir that can be constructed from a variety of plastic or metal materials. A surface of the reservoir is enclosed by a high-density, self-sealing septum, typically made of silicone rubber. Connected to the port housing is an implanted catheter which communicates with a vein or other site within the patient where the infusion of therapeutic agents is desired. Implantation of such devices generally proceeds by making a small subcutaneous pocket in an appropriate area of the patient under local anesthesia. The implanted catheter is tunnelled to the desired infusion site. When the physician desires to infuse or remove materials through the port, a hypodermic needle, which pierces the skin over the infusion port, is used and placed into the port.
Although the presently available implantable infusion ports generally operate in a satisfactory manner, they have a number of shortcomings. Since these devices rely on a compressed rubber septum for sealing and since large diameter needles can seriously damage the septum, there are limitations in the diameter of needles which can be used to penetrate the septum. These diameter limitations severely restrict the opportunities provided by the port. In cases where it is desirable to infuse drugs using a flexible external catheter, the catheter must be fed through the needle that penetrates the septum. Such catheters have an extremely small inside diameter and, therefore, impose severe limitations on both the fluid flow rate and limit the types of fibers which can be introduced.
During prolonged infusions using a conventional port, the infusion needle is taped to the patient's skin to hold it in position. Conventional pods do not allow the needle to penetrate deeply into the port. Because of this, a small displacement of the needle can cause the needle to be pulled from the port. In cases where locally toxic materials are being infused, extravasation of such materials can cause local tissue damage which itself may require corrective surgery such as skin grafting or removal of the damaged tissue.
Presently available implantable drug infusion devices also require a significant size in order to provide an acceptable target surface area for the physician who must locate the port and penetrate the septum with a needle. Since structure is required to maintain the septum in compression and provide for self-sealing after the needle is removed, the port housing becomes bulky as the septum size increases. Moreover, presently available infusion ports are difficult to clear if thrombosis occurs within the port or within the implanted catheter. This is difficult, if not impossible, because of the relative sizes of a cleaning wire which would have to be fed through the penetrating hypodermic needle in order to clear the infusion device and the internal catheter.
Present infusion ports also have a retained volume beneath the self-sealing septum. The retained volume increases the volume of drug which must be administered to enable a desired quantity to reach the infusion site. This retained volume also poses problems when a physician desires to successively deliver multiple drugs to the same infusion site, particularly when the drugs are incompatible when mixed. Additionally, when it is desired to withdraw blood through the port, the retained volume of the prior art infusion ports comprises an area where blood clotting can occur. This in turn can interfere with future access to the site. And finally, in present infusion ports, there is a risk that the physician attempting to pierce the port septum will not properly enter it, leading to the possibility of extravasation, which can cause significant undesirable consequences as mentioned above, or piercing of the implanted catheter itself.
The present invention relates to a family of implantable access pods which provide numerous enhancements over prior art devices. In accordance with this invention, an access pod is provided which incorporates the funnel-shaped entrance orifice which narrows down to a reduced diameter guide passageway. The guide passageway terminates at an internal cavity which retains a catheter valve which may be an articulating type, such as a multi-element leaflet valve assembly. The port also has an exit passageway which is connected to an implanted catheter. This specification describes numerous embodiments of alternative designs of patient access ports of the type described in the related applications.
In prior embodiments of the present invention, various valving systems were described and claimed, including leaflet valves, ball valves, "flapper" type valves, etc. Each of these valve configurations is broadly encompassed by the description "articulating catheter valve" or "articulating valve"; meaning that one or more valve elements are displaced in some predictable manner to provide access and seal around the inserted filament and to return to an original position to provide a fluid seal against backflow through the valve assembly.
In order to operate successfully, the valve mechanism of the access port must perform two distinct functions. When the valve is not being used for access, the flow of fluids in either direction through the access port is to be avoided (i.e. "normal condition sealing"). When an external catheter is placed into the port, there is a need to seal around the outer diameter of the catheter to prevent fluid from flowing out of the entrance of the access port instead of through the port exit and into the implanted catheter (i.e. "use condition sealing"). In the related applications, these two distinct sealing functions were satisfied by a single valve assembly, which as mentioned before, could be a multiple element leaflet valve assembly.
In the present invention, valve configurations are described in which features providing normal condition sealing of the access port are separated from the features which provide use condition sealing. This alternative configuration is provided in several different specific embodiments. One such embodiment utilizes a check valve in the form of an elongated tube connected to the port and having an internal passageway that is normally maintained in a flattened, occluded condition when the fluid pressure within the passageway is the same as or less than the pressure acting upon the exterior of the valve. This valve provides normal or non-use condition sealing of the passageway. An implanted internal catheter is attached to this valve and an O-ring may be located within the access device to provide an additional seal around the perimeter of an inserted filament during actual use of the device. When the external catheter has been inserted into the access device, and a fluid is being infused, the pressure within the occluded conduit is increased to the point where the passageway inflates and the fluid is delivered to the desired tissue site through the internal catheter. Other types of fluid pressure actuated valves, as further discussed below, could alternatively be used.
In another embodiment, the O-ring or perimeter sealing member may be provided downstream (or upstream) of the valve which prevents backflow through the access port in the normal condition. As used herein, the terms upstream and downstream shall be determined relative to the source for the accessing catheter.
Upon insertion of a filament through the port, the valve is opened and the filament is inserted until circumferentially engaged by the O-ring. Once such embodiment could include insertion of the accessing catheter through the collapsed tube-type of valve described above.
In yet another embodiment similar to the first described above, a ball-type check valve is utilized which provides normal condition sealing.
In another aspect of the present invention, a novel mechanism is provided to limit the extent to which a flexible filament above a predetermined diameter, such as a twenty (20) gage ANGIOCATH.TM., can be inserted through the access port. In prior embodiments of this invention, as described in the related applications, mechanisms were provided where the insertion distance of a rigid filament, such as a hypodermic needle, is limited by features designed for that purpose. One needle stop approach is to provide a bend or redirection in a passageway either before of beyond the valve assembly. The bend is such that the inserted needle would be unable to engage the valve assembly due to its rigidity. A flexible filament, however, is capable of maneuvering a bend in the passageway and as such can be inserted completely through the access port and into the implanted catheter which communicates with the desired site in the patient. There may be instances where it is desirable to provide a means of limiting the depth of insertion of a flexible filament. In some applications, engagement of the flexible filament with the internal catheter can potentially lead to dislodging of the internal catheter from the discharge fitting of the access port or repositioning it. Moreover, some implanted catheters may not have an internal diameter sufficient to accommodate the external filament.
According to the present invention, a positive stop feature is provided whereby an internal flexible filament above a predetermined size is prevented from completely passing through the access port or implanted catheter. Accordingly, the catheter stop can be utilized to form the use condition seal of the access device. Slightly, smaller diameter filaments form a seal with the internal diameter of the passageway while still being movable through the entire access port and implanted catheter. In one embodiment, the internal diameter of the passageway through the discharge fitting of the access port is convergently tapered to a diameter which is less than the external diameter of the inserted filament. During insertion, the person inserting the flexible filament will be able to feel positive engagement of the filament with the stop as further insertion is prevented. This positive stop could also be achieved by progressively decreasing the diameter of the passageway through the discharge fitting in a series of stepped reduced diameter portions. Such a progressively stepped passageway could in turn be used as a stop for certain diameter catheters. Since engagement with the positive stop feature creates a seal around the outside of the external catheter, these features can be implemented to provide use condition sealing for multiple sizes of accessing catheter, either by themselves or in conjunction with "O-rings" provided elsewhere in the port.
In accordance with another aspect of the present invention, an access port is disclosed where the implanted catheter is shielded from being inadvertently engaged by a sharp instrument such as a needle or trocar being used to access the port. Such engagement might result where the person inserting the needle or trocar completely misses the entrance orifice defined in the port. In the present invention, such a rigid accessing instrument is laterally deflected away from the implanted catheter by the exterior surface contours of the device. For example, a pair of curved surfaces can be provided on the exterior of the access port which laterally diverge from a leading edge at the device centerline. As a result, any inserted instrument inadvertently missing the entrance orifice of the port in traveling along the exterior surface of the port will engage one of the two curved surfaces and be deflected laterally away from the implanted catheter.
Various accessing approaches are possible using the access ports in accordance with the present invention including conventional needles, sharp trocars, blunt instruments, and catheter-over-needle combinations such as the ANGIOCATH.TM.. Yet another access instrument combines the skin penetration capabilities of a sharpened metal instrument with the flexibility of an external filament. These devices, also referred to as "self-introducing catheters". While all of the above filaments could be utilized with the present invention, it is believed that its greatest utility will be with a self-introducing catheter or catheter-over-needle variety.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.